fixes https://github.com/flutter/flutter/issues/138289

---

SegmentedButtom.styleFrom has been added to the segment button, so there is no longer any need to the button style from the beginning. It works like ElevatedButton.styleFrom only I added selectedForegroundColor, selectedBackgroundColor. In this way, the user will be able to change the color first without checking the MaterialState states. I added tests of the same controls.

#129215 I opened this problem myself, but I was rejected because I handled too many items in a PR. For now, I wrote a structure that only handles MaterialStates instead of users.

old (still avaliable)
<img width="626" alt="image" src="https://github.com/flutter/flutter/assets/65075121/9446b13b-c355-4d20-bda2-c47a23d42d4f">

new (just an option for developer)
<img width="483" alt="image" src="https://github.com/flutter/flutter/assets/65075121/0a645257-4c83-4029-9484-bd746c02265f">

### Code sample

<details>
<summary>expand to view the code sample</summary> 

```dart
import 'package:flutter/material.dart';

/// Flutter code sample for [SegmentedButton].

void main() {
  runApp(const SegmentedButtonApp());
}

enum Calendar { day, week, month, year }

class SegmentedButtonApp extends StatefulWidget {
  const SegmentedButtonApp({super.key});

  @override
  State<SegmentedButtonApp> createState() => _SegmentedButtonAppState();
}

class _SegmentedButtonAppState extends State<SegmentedButtonApp> {
  Calendar calendarView = Calendar.day;

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(useMaterial3: true),
      home: Scaffold(
        body: Center(
          child: SegmentedButton<Calendar>(
            style: SegmentedButton.styleFrom(
              foregroundColor: Colors.amber,
              visualDensity: VisualDensity.comfortable,
            ),
            // style: const ButtonStyle(
            //   foregroundColor: MaterialStatePropertyAll<Color>(Colors.deepPurple),
            //   visualDensity: VisualDensity.comfortable,
            // ),
            segments: const <ButtonSegment<Calendar>>[
              ButtonSegment<Calendar>(
                  value: Calendar.day,
                  label: Text('Day'),
                  icon: Icon(Icons.calendar_view_day)),
              ButtonSegment<Calendar>(
                  value: Calendar.week,
                  label: Text('Week'),
                  icon: Icon(Icons.calendar_view_week)),
              ButtonSegment<Calendar>(
                  value: Calendar.month,
                  label: Text('Month'),
                  icon: Icon(Icons.calendar_view_month)),
              ButtonSegment<Calendar>(
                  value: Calendar.year,
                  label: Text('Year'),
                  icon: Icon(Icons.calendar_today)),
            ],
            selected: <Calendar>{calendarView},
            onSelectionChanged: (Set<Calendar> newSelection) {
              setState(() {
                calendarView = newSelection.first;
              });
            },
          ),
        ),
      ),
    );
  }
}

```

</details>